Machine condition indication system

ABSTRACT

A machine condition monitor resides in close proximity to a machine train, such as an AC inductive electric motor coupled to a driven unit such as a centrifugal pump or fan. A plurality of sensing devices are connected to the machine and the machine condition monitor. Machine state and condition parameters sensed by these devices are utilized by the machine condition monitor to derive machine condition values for each component and for the machine train as a whole. These derived condition values are transmitted via an industrial communications network to a control center where they can be trended and monitored. With no particular knowledge of machine analysis techniques or severity of specific machine faults, and no special training, Operators and Production Planners can use the condition values to plan production schedules, adjust process parameters, and request appropriate maintenance action.

FIELD OF THE INVENTION

The present invention relates generally to systems and methods forcategorizing the expected dependability (i.e., productive capability) ofa machine asset. More particularly, the invention relates to a“Condition Transducer”—a sensing device for producing a value that is ananalog of machinery condition in the same way a thermocouple produces avalue that is an analog of temperature.

BACKGROUND OF THE INVENTION

Process operators, production planners, and maintenance personnel inindustrial process environments must routinely make decisions about theutilization of their production assets. They want to know the productivecapability of assets needed for successful completion of scheduledoutput. Operators and production managers routinely adjust theoperational parameters of the available assets to tune their processesfor greater efficiency, to maximize production output, or to safeguard aweakened asset in an attempt to finish a batch or production run beforea machine breaks down.

Traditionally such persons rely on the loose integration of independentsystems, input from their maintenance departments, or the advice ofexpert machine analysts. To keep abreast of machine conditions variousapproaches are utilized, such as periodic walk-around vibration programsor online continuous monitoring systems. Most of these systems focus oncollecting data that is typically transported to a central location foroffline analysis by an expert.

These systems are seldom well understood by the operators and productionplanners. They are in the domain of the maintenance or machinereliability departments and require significant training and expertise.Timely feedback which could be used to adjust the production process israrely available. A few of the online offerings attempt to provide somelocal annunciation mechanism based on limits applied to measured values,but these typically comprise merely a relay closure to light a lamp orsound an alert. This type of indication is of little use to an operatorin the control room.

Many systems rely on simple thresholds, ratios to baselines andstatistics to trigger alarms or indicate machine condition. Some systemsrely on remote host processors or other secondary systems runningsoftware expert systems to diagnose specific machine faults, but thesetechniques are typically hampered by the limited availability of dataand their remote location.

Some prior systems, such as the Distributed Diagnostic System describedin U.S. Pat. No. 6,199,018, have attempted to simplify reporting ofcondition information with green, yellow, and red indicators.Unfortunately, this does not give the operators or planners a real senseof the productive capability or stability of a machine. For example, ifa machine was operating in the green condition and goes yellow, was itrunning in the green just below the yellow threshold and now has changedonly slightly to run yellow, or has it moved from far down in the greento very high in the yellow (i.e., almost red)? If one must choosebetween whether to keep an asset active in production or alter theprocess, a machine analyst (if available) would be required to help makethe decision.

In general, the output of all these systems is discrete, which is asimple indication that further investigation is required. The onlyanalog data provided, if any, are the actual measured raw values. All ofthese approaches still require a machine fault expert who is familiarwith the criticality of specific parameters or even the seriousness ofspecific faults to make judgment calls.

What is needed, therefore, is a machine condition indication system thatproduces advisory health information in a format that an untrained andrelatively inexperienced person can successfully use to make operationalor productive capacity judgments relative to their available productionassets. Also needed is a system that provides advisory healthinformation in such a manner that it is amenable for use by automatedagents responsible for tuning a particular control system. Suchcapabilities would encourage awareness of the impact a process has onthe production assets and enable production installations to managethese assets in an informed manner, rather than running strictlyby-the-book or simply guessing.

SUMMARY

The above and other needs are met by a field-installable machinecondition indication device which reports information regarding theoperational condition of the machine to a central monitoring system. Theindication device includes sensors mounted at several locations on themachine for sensing operating characteristics and for producing sensorsignals indicative of the operating characteristics. A processor in theindication device receives the sensor signals and acquires data relatedto the operating characteristics. The processor processes the data tocalculate several characteristic parameters indicative of theoperational condition of the machine. The processor operates on thecharacteristic parameters to derive a single condition value which isindicative of the operational condition of the machine. The indicationdevice includes a communication interface for communicating thecondition value via a communication link to the central monitoringsystem.

In a most preferred embodiment, the processor of the machine conditionindication device operates on the characteristic parameters to derivethe single condition value as an analog value between 0.0 and 1.0, where0.0 indicates a failed condition and 1.0 indicates a proper operatingcondition.

In another aspect, the invention provides a method for reporting anoperational condition of a machine to a central monitoring system. Thepreferred method includes attaching vibration sensors at severallocations on the machine for sensing vibrational characteristics, andproducing vibration sensor signals that are indicative of thevibrational characteristics. The preferred method also includesattaching temperature sensors for sensing thermal characteristics, andproducing temperature sensor signals that are indicative of the thermalcharacteristics. The method further includes acquiring data from thevibration sensor signals related to the vibrational characteristics,acquiring data from the temperature sensor signals related to thethermal characteristics, and processing the data to calculate severalcharacteristic parameters indicative of the operational condition of themachine. Based on the characteristic parameters, a single conditionvalue is derived which is indicative of the operational condition of themachine, and the condition value is communicated to the centralmonitoring system.

In one preferred embodiment, the method also includes attaching a fluxsensor for sensing flux characteristics, and producing flux sensorsignals which are indicative of the flux characteristics. This preferredmethod also includes attaching a speed sensing device such as an opticalor magnetic tachometer for sensing rotational speed, and producing aspeed sensor signal indicative of the rotational speed of the machine.The method includes acquiring data from the flux sensor signal and thespeed sensor signal, and processing the data to calculate severalcharacteristic parameters of the electrical condition of the machinedriving component and the on or off state of the machine. The methodalso includes utilizing the measured rotational speed to adapt theprocess of determination of machine condition from the sensedcharacteristics according to the rotational speed of the machine.

The machine condition indication device and method described hereinaddress the shortcomings of the limited prior approaches as follows. Thesystem outputs machine condition assessments as analog values, such asfrom 0.0-1.0, which may be logically interpreted as 0 to 100%operational. The system provides fault-classification alerts whichidentify the most likely source of any detected degradation and arecommended course of preventive and/or corrective action. The conditionindication system communicates the machine condition values andfault-classification alerts over standard fieldbus wiring as anintegrated part of the control network. Using inherent capabilities of atypical process control system, the condition values may be trended forrate of change, monitored for correlated changes when productionparameters are altered, compared for variation between machineoperators, and be applied against alarm thresholds. But mostimportantly, relatively inexperienced and less trained individuals canreasonably interpret the significance of the condition values andfault-classification alerts and respond appropriately.

The machine condition indication system holistically combinesinformation from all measurements and from all components of the machinetrain. This evaluation occurs locally and autonomously in a deviceinstalled near the monitored machinery. A change in a single conditionparameter that would typically cause other systems to generate an alarmis assessed by the system for relevance in light of all other knowninformation with the potential of modifying its impact on the conditionvalue or perhaps affecting the severity of an alert. In addition to themagnitude of a change, the types of any detected machine faults alsohave a varying impact on the machine condition and fault severityoutput. Obviously, not all conditions have the same potential impact,require the same immediacy of attention, or influence the operation ofthe machine in the same manner. Logically, combinations of faults andseverity of changes in machine conditions must also be factoreddifferently.

Unlike many machine monitoring systems which utilize a static baselinefor applying alarm criteria, the present invention uses an adaptive“smart” baseline signature vector of measured characteristics. Itcontinually evaluates the baseline to judge whether it is trulyrepresentative of the “normal” state of the asset being monitored andwhether the baseline vector components should be adjusted up or down toa new set of values. Unlike systems that rely solely on fixed orstatistically derived thresholds to trigger alarms, this inventionheuristically combines a multiplicity of factors to determine the degreeof degradation, rate of degradation and a relative condition severity.

It is envisioned that the analog machine condition information providedby the invention will be fully integrated into the process environmentin the same manner as any other standard sensing device, such astemperature or pressure transducers. Although operators have long hadvisibility into the production process itself, this invention seamlesslymerges advisory information about the underlying process machinery intothat window of visibility.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention are apparent by reference to thedetailed description when considered in conjunction with the figures,which are not to scale so as to more clearly show the details, whereinlike reference numbers indicate like elements throughout the severalviews, and wherein:

FIG. 1 depicts a functional block diagram of a network of machinecondition monitoring devices according to a preferred embodiment of theinvention;

FIG. 2 depicts a functional block diagram of a machine conditionmonitoring device according to a preferred embodiment of the invention;

FIG. 3 depicts a flow diagram representing a process for monitoring thecondition of a machine according to preferred embodiments of theinvention; and

FIG. 4 depicts a graph of early detector severity versus increase ofaverage parameter value according to preferred embodiments of theinvention.

DETAILED DESCRIPTION

FIG. 1 depicts an exemplary machine condition monitoring system 10constructed in accordance with certain aspects of the present inventionis illustrated. In general, the exemplary machine condition monitoringsystem 10 is coupled to one or more machines 12. The system 10 comprisesone or more condition reporting devices 14 coupled to a correspondingone of the machines 12. In the exemplary system of FIG. 1, each of themachines 12 is represented as a conventional AC induction motor directlycoupled to a centrifugal pump, although the present invention isapplicable to other machines such as fans, compressors, brushless DCmachines, switched reluctance machines, and the like.

Each of the condition reporting devices 14 collects informationconcerning the operational status of the machine 12 with which it isassociated. For example, each condition reporting device 14 may collectinformation concerning the vibrational characteristics of the machine12, the temperature of the stator, windings and/or bearings of themachine 12, the flux established in the stator and rotor, and therotational speed of the machine 12. This information may be stored indata storage elements within the condition reporting devices 14.

In the preferred embodiment, the collected information concerning eachof the various machines 12 is processed by an associated conditionreporting device 14 to produce a status indication reflecting theoperational status of the associated machine 12. Preferably, this statusindication takes the form of a numerical condition indicator of between0.0 and 1.0 that is reported to one or more computers 15 via acommunication network 17. If the machine 12 is operating properly, anumber near 1.0 will be reported. If the machine 12 appears to beoperational but in a partially degraded state of possible interest tothe operator or requiring maintenance soon, a number around 0.5 will bereported. If the machine 12 is in a seriously degraded state or hasfailed, a number near 0.0 will be reported. The condition reportingdevices 14 may also pre-process some or all of the collected informationfor external communication to, and later processing by, other computersin the system 10.

In some embodiments, communication between the devices 14 and thecomputers 15 is enabled by protocol translators 13, such as depicted inFIG. 1.

In one embodiment, each of the condition reporting devices 14 includes amicrocontroller or microprocessor that runs software establishing alocal, diagnostic model. The diagnostic model receives the collectedinformation and, using the local model, indicates the condition of themachine. In this embodiment, the parameters that define the local modelmay be downloaded to the condition reporting devices 14, such as fromthe computers 15 in the system 10.

As shown in the example of FIG. 2, each condition reporting device 14includes a communications board 16 that is adapted to communicate (i.e.,transmit and receive) information and data over an appropriatecommunications link 18. In the preferred embodiment, the communicationsboard 16 includes appropriate hardware, software and/or firmware toallow the communications board 16 to receive and transmit information onthe link 18 according to one or more appropriate protocols. For example,the communications board 16 may be adapted to communicate using wirelesscommunication techniques, or using standard communication protocols suchas the HART™, CT Net™, Modbus+™, Profibus™ protocols, FOUNDATION™fieldbus or other similar protocols. The communications board 16 may beconstructed and configured using known devices and techniques, and theappropriate construction of such a board will be apparent to those ofordinary skill in the art having the benefit of this disclosure.

Coupled to the communications board 16 is a main control board 20 that,in the exemplary embodiment of FIG. 2, includes a microprocessor ormicrocontroller 22 and a data storage device 24. In one embodiment, themicroprocessor 22 is a Motorola MC68LC302, HC11 or HC05 type processorand the data storage device 24 comprises flash memory, such as a flashmemory device contained within the microprocessor 22 or an externalflash memory device. Other memory devices, such as EPROM and DRAMdevices may be used in conjunction with the microprocessor 22 toimplement the system described herein. The construction of the maincontrol board 20 and the selection of the appropriate memory deviceswill be apparent to one of ordinary skill in the art having the benefitof this disclosure.

In a preferred embodiment, a modem device 26, such as an RS-485 modem,is also coupled to the microprocessor 22 such that the microprocessorcan communicate over the modem device 26. In the exemplary embodiment ofFIG. 2, additional communication devices are provided to allow themicroprocessor 22 to communicate data and information. Specifically, anRF transceiver 28 is provided to allow for “wireless” communications anda HART™ ASIC 30 or other appropriate device (e.g., a FR 3244transmitter) is provided to allow for the microprocessor 22 tocommunicate using the HART™ protocol. Those of ordinary skill in the artwill appreciate that the communication devices 26, 28 and 30 are onlyexamples of the types of communication devices that may be used withmicroprocessor 22 and that other devices (and other combinations ofdevices) may be used. Embodiments are also envisioned whereincommunication devices such as devices 26, 28 and 30, are eliminated andall microprocessor communications are accomplished through a CT protocolboard 31.

In certain embodiments, a dual-port memory device 32 (e.g., a dual portRAM) may be positioned between the microprocessor 22 and the variousdevices used by the microprocessor for communications. FIG. 2illustrates the use of such a device 32 in the communications linkbetween the microprocessor 22 and the communications board 16. In otherembodiments the connection between the microprocessor 22 andcommunications board 16 may be accomplished using DMA mechanisms, serialdata interface, parallel data interface or any other typical methodwhich would be apparent to those of ordinary skill in the art.

As depicted in FIG. 2, the microprocessor 22 is adapted to receiveinformation provided from a sensor set adapted to sense variousoperating parameters related to the condition of the machine 12. FIG. 2illustrates one such exemplary sensor set including twelve sensors: 34a-34 d, 36 a-36 f, 38 and 40.

Sensors 34 a-34 d are preferably RTD transducers that are positionedappropriately with respect to the machine 12. In one embodiment, two ofthe RTD transducers 34 a-34 d are positioned near two bearing deviceswithin a machine 12 and other of the RTD transducers are positioned todetect the temperature of the windings of machine 12, the temperature ofthe machine housing, and/or the temperature of the environment in whichmachine 12 is operating. The precise placement and use of such RTDtemperature and vibration sensors will vary from application toapplication, and those of ordinary skill in the art will appreciate thatfewer or more than four RTD transducers may be used to implement theteachings contained herein. Also, those of ordinary skill in the artwill appreciate that temperature detection devices other than RTDtransducers may be used to detect and provide information concerning thetemperature of machine 12, its bearings, housing and/or environment.

In the embodiment of FIG. 2, the microprocessor 22 includes a pluralityof built-in A/D converters 42 coupled to the RTD transducers 34 a-34 d.Each of the RTD transducers 34 a-34 d preferably comprises an RTD devicewith an amplifier that receives and conditions the output signal of theRTD device such that it is a signal within the range acceptable for theappropriate A/D converter 42 of the microprocessor 22. In embodimentswhere a microprocessor 22 not having built-in A/D capabilities isutilized, one or more separate A/D converters, and possibly separatecommunications devices, may be coupled between the RTD transducers 34a-34 d and the microprocessor 22.

In addition to the RTD transducers 34 a-34 d, the microprocessor 22preferably also receives output signals from vibration sensors 36 a-36 fthat, in the embodiment of FIG. 2, include vibration detectors coupledto amplifiers for proper conditioning of the vibration signals in amanner similar to the conditioning associated with the RTD transducersdiscussed above. The vibration sensors 36 a-36 f may be positioned withrespect to the machine 12 to detect mechanical vibrations (or theabsence of such vibrations) from the machine 12 that are induced whenthe machine 12 is running and/or at rest.

In the embodiment of FIG. 2, the microprocessor 22 also receives theoutput signals from an electromagnetic flux sensor 38 that includes aflux sensing device and a conditioning amplifier. In general, the fluxsensor 38 should be positioned appropriately with respect to theassociated machine 12 to detect the magnitude of the flux existing inthe stator of machine 12. As those skilled in the art will appreciate,the flux sensor 38 allows for a determination of the rotor speed, theload of the machine 12, and the conditions of the rotor bar and statorwindings, among other things.

As shown in FIG. 2, the microprocessor 22 also preferably receivesoutput signals from a speed indicating sensor 40, such as an opticaltachometer, that produces a signal representative of the rotationalspeed of the machine 12.

In the preferred embodiment of the invention depicted in FIG. 2, thesignals produced by vibration sensors 36 a-36 f, the flux sensor 38, andthe speed sensor 40 may be acquired in parallel by the use of multipleA/D converters 44. As depicted in FIG. 2, these additional A/Dconverters 44 may be coupled to the microprocessor 22 by a digitalsignal processor (DSP) 50. The embodiment of FIG. 2 also includes aninternal memory 52 controlled by the DSP 50 for buffering the collectionof signal data from the sensors. The synchronously collected data maythen be transferred to the microprocessor 22 via a communications link54. Preferably this link is a DMA transfer, but those of ordinary skillin the art will appreciate that many other standard techniques exist formoving blocks of data between processors.

The simultaneous collection of signal data from the sensors 36 a-36 f,38, and 40 simplifies the subsequent analysis as will be appreciated byone skilled in the art of machine condition analysis. It will also beapparent that data could also be collected from the sensorssequentially.

The selection, construction, and positioning of sensors 34 a-34 d, 36a-36 f, 38, and 40, and the coupling of such sensors to microprocessor22, will be apparent to those of ordinary skill in the art having thebenefit of this disclosure. Sensors other than those discussed above maybe used without departing from the teachings herein. For example, othersensor types (e.g., current and/or voltage sensors) may be added orsubstituted as required for reliability or cost optimization or tobetter acquire various desired operational characteristics.

From vibration and flux measurements taken at strategic locations on themachine 12, the calculated characteristics of interest can give anindication of present or developing problems relating to bearing fatigueand failure, cavitation/turbulent flow, improper lubrication, imbalance,misalignment, and mounting soft-foot, as well as basic motor problemsassociated with slot pass frequencies. Some basic motor problems canalso be indicated by excessive heating observed from temperaturereadings. To provide an indication of such motor problems, the machinecondition monitor implements, among other things, the analysistechniques listed in Table I. TABLE I Machinery Condition MonitoringEnvironment Raw data The system uses high sample rate, long acquisitioncollection time, and multi-channel time synchronous operation.Characteristic The system uses arbitrarily complex relationships,Calculations optimized domain-specific intrinsics, a full range ofarithmetic capabilities, and downloadable extendable calculation sets.Time Waveform The system applies mean, minimum, maximum, span Techniques(peak-to-peak), absolute peak, variance, skewness, kurtosis, RMS(standard deviation), crest factor, autocorrelation, and timesynchronous waveform techniques. Frequency The system applies discreteFourier transform Techniques (SF, FFT), peak, phase, power, energybands, (including synchronous (harmonic families) and non- order-based)synchronous (inharmonic) energy (even, odd, both, range), sidebands(upper, lower, both, even, odd, bom) frequency techniques. AdditionalThe system uses windowing, averaging, interpolation Analytical anddecimation, dynamic filters (FIR, IIR), Methods convolution, peak groupsignatures, energy distributions, extreme low-frequency, digitalintegration and differentiation, cross-channel (wobble andeccentricity), joint time-frequency, cepstrum, wavelets, demodulation,and PeakVue ® analytical methods. Historical Data The system applieshistorical data management, Management including multilevel temporalstatistical characterization (minimum, maximum, mean, median, moments,Z), correlation, regression, trend fitting, statistical means analysis,and querying for short/ long-term characterization of a value accordingto hour/shift of day, day of week, week of month/year, month/quarter ofyear. Inference The system inference environment uses finite stateEnvironment automata, directed graph, hybrid cognitive mesh (from fuzzycognitive map & neural net techniques), dynamic fuzzy surface (runtimesets adaptive to data in several dimensions), calculated atoms(characteristic expression results), activation axons (active transitionlinks between nodes), proposition nodes, rich calculation environment tosupport dynamic heuristics (GA-capable - new propositions can beprogrammatically composed dynamically and executed at runtime), anddownloadable extendable inference sets; approximately equivalent tocalculating a multi- dimensional vector whose magnitude representsseverity/urgency and whose “direction cosines” identify the possiblecondition most similar to the current “signature.”

A process for analyzing a machine's condition and generating machinecondition information is depicted in FIG. 3. In the preferred embodimentof the invention, this machine condition analysis procedure is performedby the microprocessor 22 to provide a rapid screening of data associatedwith the overall condition of the machine 12 under test.

To illustrate the apparatus and method of this invention, the followingrepresentative example is provided. Upon initiation of the device 14, aninitial baseline reference set of data is acquired (steps 102-110 ofFIG. 3). Preferably, baseline or running average data is not acquireduntil at least about 30 seconds after machine start-up. Acquisitionspreferably consist of a 0-40 kHz time waveform with an associatedspectrum from each sensor 36 a-36 f, 38, and 40 (step 102). Theappropriate operational characteristic parameters are then calculatedand trended (steps 104 & 106). Examples of possible calculations in apreferred embodiment of this invention are listed in Table II. Theequations provided are typical rather than exhaustive. TABLE IICharacteristic Parameter Description Time Waveform-based Peak-to-PeakAlso known as the signal span. Determined by locating W_(max) andW_(min) (the largest positive-going and the largest negative-goingexcursions in amplitude from the waveform mean) and calculating: Pk2Pk =W_(max) − W_(min) Root Mean Square Also known as the standard deviation.Determined (RMS) as the square-root of the sum of the squared meandifference for each sample in the waveform.$\overset{\_}{w} = {\frac{1}{N}{\sum\limits_{n}W_{n}}}$${RMS} = \sqrt{\frac{1}{N}\quad{\sum\limits_{n}\left( {W_{n} - \overset{\_}{w}} \right)^{2}}}$Crest Factor Determined as the ratio between the largest absoluteexcursion from the mean of the waveform and the RMS value.${CF} = \frac{\max\left( {{{W_{\max} - \overset{\_}{w}}},{{W_{\min} - \overset{\_}{w}}}} \right)}{RMS}$Frequency Spectrum-based Mid-band energy Summation of the energy foundbetween 1 kHz and 10 kHz in the Fourier transform of the waveform;square-root of the sum of power in the spectrum.${E\quad 1k\quad 10\quad k} = \sqrt{\sum\limits_{f = {1\quad k}}^{10\quad k}{{\mathfrak{F}}_{f}}^{2}}$High-band energy Summation of the energy found between 10 kHz and 40 kHzin the Fourier transform of the waveform; square-root of the sum ofpower in the spectrum.${E\quad 10k\quad 40\quad k} = \sqrt{\sum\limits_{f = {1\quad 0k}}^{40\quad k}{{\mathfrak{F}}_{f}}^{2}}$Low-band energy Summation of the energy, digitally integrated from (asVelocity) acceleration to velocity, found below 1 kHz in the Fouriertransform of the waveform.${LowFreqVel} = \sqrt{\sum\limits_{f = \Delta}^{1k}\left( \frac{61.45\quad{\mathfrak{F}}_{f}}{f} \right)^{2}}$

In addition, energy from a slot pass family parameter is calculated asneeded. Preferably, the slot pass frequency parameters, such as thoselisted in Table III, are used only as a special test. TABLE IIIPrinciple Slot PSP_(RotoBar) = RotorBars · Z_(Hz) + μ · L_(Hz) PassingFrequency Z_(Hz) = Fundamental Turning Frequency (Rotor Bars)$\mu = \left\{ \begin{matrix}{0,{vibration}} \\{1,{{{current}\&}\quad{flux}}}\end{matrix} \right.$ L_(Hz) = Line Frequency Principle SlotPSP_(Stator) = StatorSlots · Z_(Hz) + μ · L_(Hz) Passing FrequencyZ_(Hz) = Fundamental Turning Frequency (Stators)$\mu = \left\{ \begin{matrix}{0,{vibration}} \\{1,{{{current}\&}\quad{flux}}}\end{matrix} \right.$ L_(Hz) = Line Frequency 2xLF Family of Slot PassFrequencies $\begin{matrix}{{2{xLF}} = {{\sum\limits_{{n = 0},2,4,6,8,10}{PSP}} \pm {n \cdot L_{Hz}}}} \\{{PSP} = \left\{ {{PSP}_{RotorBar},{PSP}_{Stator}} \right\}} \\{L_{Hz} = {{Line}\quad{Frequency}}}\end{matrix}\quad$

Based on a known number of rotor bars and stator slots of the machine12, and the known speed of the machine 12, the device 14 calculatesPSP_(ROTORBAR) and PSP_(STATOR) for each measurement on the machine 12.The device 14 then determines the 2xLF family of slot passingfrequencies relating to both types of slot pass frequencies as describedin Table II. If the machine 12 is operating within normal parameters,spectral peaks should be within ±0.25% of the expected frequency. Insome embodiments, the energy of the largest PSP peak and two sidebandson either side of PSP is also calculated.

If neither the number of rotor bars nor stator slots is known, thesystem 10 calculates the 2xLF family of slot passing frequencies asfollows: (1) locate the largest peak in the spectrum between 1 kHz and10 kHz; (2) search for sidebands about the largest peak spaced at 2xLF(within ±0.25%); (3) locate two peaks on either side of the largestpeak; and (4) determine the energy of this family.

One of the first analysis requirements in determination of machinecondition is to use valid data. Accordingly, the device 14 uses severalkey boundary threshold values which act as data screening qualifiers,examples of which are listed in Table IV. TABLE IV Value Purpose EDefines the type of environment in which the machine- under-testoperates as either E_(smooth), E_(rough) or E_(normal). Based on thevalue E, the system modifies its expectations of the energy levels andvariance expected for the analysis, and adjusts its sensitivity andfault conclusions accordingly. D Defines the size (depth) of a baselinepopulation. Preferably, there is a different D value for each parameterfor each operating environment. O Defines the “order” of a “lag filter”used to decide that a change in a parameter is significant. When thesystem detects a significant change, there must be O consecutive valuesbefore the change filters through to the analysis. There is preferably adifferent O value for each parameter for each operating environment. N Aparametric scaling factor which helps define the width of the “steady”region around a baseline as well as the severity of any change.Preferably, there is a different N value for each parameter for eachoperating environment. M A parametric sigma scaling factor that helpsdefine the width of the “steady” statistical region around a baseline.In the preferred embodiment, there is a different M value for eachparameter in each operating environment. Min_(reading) The smallestallowable RMS waveform value. If readings are below this value, themeasurement is considered bad. There is preferably a differentMin_(reading) value for each parameter in each operating environment.Min_(diag) The baseline value of a parameter which must be exceededbefore diagnostic analysis will be performed. Levels below this pointare considered too low to be significant. There is preferably adifferent Min_(diag) value for each parameter in each operatingenvironment. Min_(delta) The analysis value that defines classificationregions parametrically. This value places a limit on how small a changewill be detected and passed through as significant. Preferably, there isa different Min_(delta) value for each parameter in each operatingenvironment. Min_(alarm) Defines the point at which parametric alarmsbegin to affect the analysis results. In the preferred embodiment, thereis a different Min_(alarm) value for each parameter for each operatingenvironment. Min_(alway) Defines a point beyond which any value isconsidered to trigger analysis; i.e., a meaningful “increase” in thevalue. However, the requirement of O_(E) consecutive increasing valuespreferably still applies. There is preferably a different Min_(always)value for each parameter for each operating environment.

Table V indicates how the boundary threshold values will be applied toeach characteristic parameter based on the classification of the machineoperating environment as normal, smooth, or rough. TABLE V E E_(normal)E_(smooth) E_(rough) D D_(normal) D_(smooth) D_(rough) O O_(normal)O_(smooth) O_(rough) N N_(normal) N_(smooth) N_(rough) M M_(normal)M_(smooth) M_(rough) Min_(reading) Min_(reading normal)Min_(reading smooth) Min_(reading rough) Min_(diag) Min_(diag normal)Min_(diag smooth) Min_(diag rough) Min_(delta) Min_(delta normal)Min_(delta smooth) Min_(delta rough) Min_(alarm) Min_(alarm normal)Min_(alarm smooth) Min_(alarm rough) Min_(always) Min_(always normal)Min_(always smooth) Min_(always rough)

In the preferred embodiment of the invention, each characteristicparameter has a baseline population for evaluation which consists of thevalue as calculated from <N=D_([E])> contiguous data acquisitions. Atthe end of N acquisitions, the population for each parameter iscollapsed into a candidate pair<A_(base), σ_(base)>which represent the“normal” expectation for that parameter as indicated in FIG. 3 (step110). This process preferably continues as long as the device 14 isrunning. After every N acquisitions, the population is preferablycollapsed and a new candidate pair<A_(new), σ_(new)> is formed. If thenew candidate value Anew is valid and lower than the current baselinevalue Abase, the new value Anew becomes the active baseline. Similarly,if the new value anew is valid and “tighter” than the current valueσ_(base), the new value σ_(new) becomes the active baseline. This may beexpressed as:if (A_(new)>Min_(diag)) and (A_(new)<A_(base)) then A_(base)=A_(new)if (σ_(new)>Min_(diag)) and (σ_(new)<σ_(base)) then σ_(base)=σ_(new)

Periodically the active baseline information for all parameters is savedto non-volatile storage so that in case of power failure recovery, themonitoring device 14 will be able to restart analysis more quickly.

Similarly, according to a preferred embodiment, a weighted runningaverage is kept based on the formula:A _(i)=0.8A _(i-1)+0.2x _(i).where x_(i) is the calculated value of the particular parameter for thecurrent iteration. At i=0, or whenever a new baseline is chosen, A_(i)is set equal to A_(base). This running average is preferably used totrack baseline divergent trends and frame-to-frame step changes inparameters.

In the preferred embodiment, each instantaneous (current) parametervalue is checked against a series of bounded regions for preliminaryclassification: $\begin{matrix}{{x_{i}} \notin \left\lbrack {\frac{A_{base}}{N_{\lbrack E\rbrack}},{A_{base} \cdot N_{\lbrack E\rbrack}}} \right\rbrack} & (1) \\{x_{i} \notin \left\lfloor {{A_{base} - {M_{\lbrack E\rbrack}\sigma_{base}}},{A_{base} + {M_{\lbrack E\rbrack}\sigma_{base}}}} \right\rfloor} & (2)\end{matrix}$

In the following discussion, the condition of a parameter value beingclassified as UP (increasing) or being classified as DOWN (decreasing)is defined as follows:

[parameter value satisfies equations (1) and/or (2) above

-   -   AND    -   parameter value>Min_(alarm [E])    -   AND

parameter value discrepancy magnitude>Min_(delta [E])]OR

parameter value>Min_(always [E].)

The condition of a parameter being classified as STEADY is equivalent toNOT (UP or DOWN).

Early detector severity versus increase in average characteristicparameter value is depicted in the graph of FIG. 4. The range ofseverity from 25% to 100% is scaled by the parametric values from TableIV associated with the currently selected operating environment asdefined in Table V.

In the following discussion there are numerous statements of the form:if <P> is <C> then <R> is <V>where <P> is a measured or calculated characteristic parameter asdescribed in Table II or III; where <C> is a particular possible faultclassification according to the model; where <R> is an accumulatingresult variable or partial conclusion to be reached based on thesimilarity of <P> with <C>; and where <V> is a transfer function to beapplied to <R> such that the strength of the conclusion is modeled onthe similarity of <P> with <C>.

Multiple implication clauses, such as <P> is <C>, may occur in a singlesimilarity statement. Multiple consequence clauses, such as <R> is <V>,may occur in a single similarity statement. Multiple results <R> may beaffected by a single transfer function <V>. In higher level meshes, theinput <P> may be the output <R> of a previous similarity statement. Inthat case, the result is the similarity of the partial conclusion withthe classifier concept <C>.

Each similarity statement is an edge in a multiply-connected directedgraph forming a mesh. The edge may be viewed as a zener diode whichprevents conduction up to a threshold and then begins conducting. Theimplication clause of the statement represents the biasing threshold andthe consequence clause represents the passed voltage.

Each node in the graph represents a set of possible partial conclusionswhich can be reached based on the similarity of one or more incomingedges to their implication clauses. A conclusion node will “fire” to theextent that one or more consequence clauses “conduct” and the strengthof the edge's output defines its “belief” in the conclusion(s)represented by the node. The “bulge” of a particular node in theimplication mesh is a combination of any incoming edges to the extentthey have exceeded their “bias voltage” and the back-pressure from anyoutgoing edges which are not yet “conducting” to the extent that theyare under their “bias voltage”.

The resultant for each component implication mesh is derived using a“preponderance of evidence” evaluation of all the intermediateconclusions so accumulated to determine the “potential field” aroundeach possible fault classification. The most likely condition, if any,is enunciated in a fault-classification alert for the component. Thecondition indication values of the individual components are derived bycalculating the magnitude of a severity-weighted degradation vector andsubtracting the result from 1.0 to produce an approximation to thecomponent condition.

The overall condition conclusion for the machine as a whole is derivedfrom the individual component contributions as a cascade in a similarfashion. Additional parameters which are not component specific, andpartial conclusions at the component level which can not be adequatelydifferentiated, are also taken into consideration such that the overallcondition indication value reported by the device 14 varies fairlyindependently from the condition indication values of the components.Additional fault-classification alerts may be produced and enunciated atthe overall level in addition to any produced by the individualcomponents.

The entire inference mechanism may be extended or replaced bydownloading new characteristic parameter calculation descriptions, newparameter-controlling threshold values, new fault classificationdescriptions, new partial conclusion nodes, new activating edges, and/orentirely new implication mesh definitions from a computer 15.

The following diagnostic path is an instructive example showing how thedevice 14 uses multiple data sources and multiple parameters at eachsource to derive overall conclusions regarding machine conditions. Theparticular example provided is specific to an AC induction motor coupleddirectly to a centrifugal pump. It will be apparent to those skilled inthe art that the techniques disclosed herein may also be applied to manyother machinery configurations without departing from the teachingsherein.

Initial conclusion confidence percentage (weighting) values for thesimilarity transfer function <V> (as represented below by X) aremultiple different values that are utilized. These values X areempirically derived through historical experience and are inherent inthe model.

They may be varied according to the application and installation. Theinvention also encompasses mechanisms for learning new values X from acombination of user configuration parameters and historical dataacquired as a natural consequence of the operation of the device 14 asdescribed in FIG. 3, and particularly step 106.

Preliminary Validation (All Sensors)

-   1. if RMS is TOOSMALL    -   then SENSORGONE is Confidence X %-   2. if RMS is DOWNSIGNIFICANTLY    -   then SENSORGONE is Confidence X %-   Preliminary Per Sensor Diagnostics (All Components)-   1. if E1k10k is UP and E10k40k is STEADY    -   then BRGFAILDEGRADE is Confidence X %-   2. if E1k10k is STEADY and E10k40k is UP    -   then BRGLUBEFATIGUE is Confidence X %-   3. if LowFreqVel is UP    -   then (MISALIGNMENT, IMBALANCE, LOOSENESS) is Confidence X %        Pump-Specific Diagnostics, Per-Sensor-   1. if E1k10k is STEADY and E10k40k is UP    -   then CAVITATION is Confidence X %-   2. if E1k10k is Up and E10k40k is UP    -   then CAVITATION is Confidence X %-   3. if CrestFactor is UP and E1k10k is UP and E10k40k is STEADY    -   then BRGFAILDEGRADE is Increased X %-   4. if CrestFactor is UP and E1k10k is STEADY and E10k40k is UP    -   then {CAVITATION, BRGLUBEFATIGUE} is Increased X %-   5. if Pk2Pk is UP and CURRENTFAULTS is EMPTY then GENVIBRATION is    Confidence X %    Pump Overall Diagnostics-   1. if InboardBearing(E1k10k) is UP and OutboardBearing(E1k10k) is UP    -   then CAVITATION is Increased X %-   2. if InboardBearing(E10k40k) is UP and OutboardBearing(E10k40k) is    UP    -   then CAVITATION is Increased X %-   3. if InboardBearing(E10k40k) is UP and OutboardBearing(E10k40k) is    STEADY    -   then BRGLUBEFATIGUE is Increased X %-   4. if InboardBearing(E10k40k) is STEADY and OutboardBearing(E10k40k)    is UP then BRGLUBEFATIGUE is Increased X %    where InboardBearing(parameter) is the value of the specified    characteristic parameter as calculated from signal data collected at    a sensor placed near the inboard bearing on the pump being monitored    by the device 14. OutboardBearing(parameter) is the value of the    characteristic parameter as calculated from signal data collected at    a sensor placed near the outboard bearing on the pump being    monitored.-   5. if CAVITATION is INDICATED but Specific Gravity of Pumped Fluid>Z    -   then CAVITATION is Decreased X %        where Z is a configuration value inherent to the model. The        value Z may be varied according to the installation based on an        application handling various materials.        Motor-Specific Diagnostics, Per-Sensor-   1. if E1k10k is Up and E10k40k is STEADY    -   then ECCSOFTFTRTRBAR is Confidence X %-   2. if E1k10k is Up and E10k40k is UP    -   then {BRGLUBEFATIGUE, BRGFAILDEGRADE, ECCSOFTFTRTRBAR} is        Confidence X %-   3. if CrestFactor is UP and E1k10k is UP and E10k40k is STEADY    -   then BRGFAILDEGRADE is Increased X %-   4. if CrestFactor is UP and E1k10k is STEADY and E10k40k is UP    -   then BRGLUBEFATIGUE is Increased X %-   5. if Pk2Pk is UP and CURRENTFAULTS is EMPTY    -   then GENVIBRATION is Confidence X %        Motor Overall Diagnostics-   1. if InboardBearing(E10k40k) is UP and OutboardBearing(E10k40k) is    STEADY    -   then BRGLUBEFATIGUE is Increased X %-   2. if InboardBearing(E10k40k) is STEADY and OutboardBearing(E10k40k)    is UP    -   then BRGLUBEFATIGUE is Increased X %        where InboardBearing(parameter) is the value of the specified        characteristic parameter as calculated from signal data        collected at a sensor placed near the inboard bearing on the        motor being monitored by the device 14, and        OutboardBearing(parameter) is the value of the characteristic        parameter as calculated from signal data collected at a sensor        placed near the outboard bearing on the motor being monitored.        Eccentricity

For situations where eccentricity is suspected, the device 14 calculatesthe energy of the 2xLF family of slot pass frequencies (2xLF_SPF) asdescribed in Table III and subtracts this energy from the 1 kHz-10 kHzspectral energy parameter (E1k10k). If the resulting parameter valuestill qualifies as being UP (i.e., an increase is observed), theneccentricity is ruled out. If the resulting parameter value nowqualifies as STEADY (i.e., no increase is observed), then the problem isprobably related to eccentricity. This determination may be expressed asfollows:

-   1. if E1k10k is Up and (E10k40k is STEADY or E10k40k is UP) and    (E1k10k−2xLF_SPF) is UP    -   then ECCSFTFTRTRBAR is Excluded-   2. if E1k10k is UP and (E10k40k is STEADY or E10k40k is UP) and    (E1k10k−2xLF_SPF) is STEADY    -   then BRGFAILDEGRADE is Decreased X %        Machinery Overall Diagnostics Refinements-   1. if PumpInboard(E1k10k is STEADY and E10k40k is UP) and    -   MotorInboard(E1k10k is STEADY and E10k40k is UP)    -   then CAVITATION is Excluded, GENVIBRATION is Confidence X %-   2. if PumpInboard(E1k10k is UP and E10k40k is UP) and    -   MotorInboard(E1k10k is UP and E10k40k is STEADY)    -   then CAVITATION is Unlikely, GENVIBRATION is Confidence X %        where MotorInboard(parameter) is the value of the specified        characteristic parameter as calculated from signal data        collected at a sensor placed near the inboard bearing on the        motor of the machine being monitored by the device 14, and        PumpInboard(parameter) is the value of the specified        characteristic parameter as calculated from signal data        collected at a sensor placed near the inboard bearing on the        pump of the machine being monitored.

The core operation of the device 14, and in particular the processingassociated with the inference mechanism described herein, is depicted inFIG. 3. Once operational, the analytical portion of device 14 proceedsiteratively according to a frame-based pattern. Prior to the begin step,any configuration parameters which may have been changed by the computer15 are copied for reference during the frame. This isolates the framefrom possible disruption and ensures the computational integrity of eachframe. Any pending data transmission requests are processed after thefinish step. This ensures that data transmitted as a group comes from asingle iteration of the process frame and is internally consistent.

Steps 102, 104, and 106 of the preferred embodiment of the invention arepreparatory in nature and are preferably performed prior to theprocessing associated with the inference mechanism. Step 106 providesthe contribution of each measured or calculated characteristic parameterto a historical record of that particular parameter over time. This isdone in a hierarchical cascade of statistical groupings where eachchained population is built on the preceding one. Whenever a particularsample population fills up, the set of sample values is collapsed into astatistical representation which constitutes a single representativesample for the next higher set. The contents of the lower set is thenreset and begins accumulating a new set of samples. This forwardpropagation of statistical characterizations continues until a finalpredefined superset has been reached. An example would be a lowest levelset which holds sixty (60) samples and represents one hour's worth ofcollection at a one minute granularity. The next higher level set holdstwenty-four (24) samples and represents one day's worth of collection;i.e., twenty-four “overflow cycles” of the lower set.

Step 108 involves determining which inference mesh components shouldcontribute in the current frame cycle based on sensor status, machineon/off state, etc.

Step 112 provides a notification to all eligible components that aregoing to participate in the current iteration. This allows them to“bind” current configuration parameters, threshold values, etc. whichare necessary to dynamically calculate the similarity statements.

Step 114 is a cascaded calculation of all eligible inference elementsstarting from the lowest (independent variables) and proceeding upwardsthrough the similarity statements contained in activating edges, throughthe partial conclusion nodes, and finally into the condensing processfor the overall mesh as described previously.

Step 116 provides a notification to all affected components that theirparticipation has completed. This provides an opportunity to “clean up”and release any temporary resources as appropriate.

In step 118, the component-level condition values and the overallmachine condition value are calculated.

Step 120 provides a point where all data produced in the frame isconsistent, and any automatic export of fault-classification alerts,condition values, or intermediate results may safely occur withoutdanger of inadvertent corruption by competing threads of execution.

The foregoing description of preferred embodiments for this inventionhave been presented for purposes of illustration and description. Theyare not intended to be exhaustive or to limit the invention to theprecise form disclosed. Obvious modifications or variations are possiblein light of the above teachings. The embodiments are chosen anddescribed in an effort to provide the best illustrations of theprinciples of the invention and its practical application, and tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as is suited tothe particular use contemplated. All such modifications and variationsare within the scope of the invention as determined by the appendedclaims when interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

1. A method for determining an operational condition of a machine,comprising: (a) accepting data representing sensor signals acquired froma plurality of sensors attached to the machine, where the sensor signalsare indicative of operational characteristics of the machine; (b)processing the data to calculate a plurality of characteristicparameters indicative of the operational condition of the machine; and(c) operating on the characteristic parameters to derive a singlecondition value which is indicative of the operational condition of themachine.
 2. The method of claim 1 wherein step (b) further comprisesprocessing the data to calculate a plurality of waveform-basedcharacteristic parameters.
 3. The method of claim 1 wherein step (b)further comprises processing time waveform data to calculate frequencyspectral data using discrete Fourier transform techniques.
 4. The methodof claim 3 further comprising processing the frequency spectral data tocalculate a plurality of frequency-based characteristic parameters. 5.The method of claim 4 further comprising processing the frequencyspectral data to calculate the plurality of frequency-basedcharacteristic parameters using order-based techniques dependent on therotational speed of the machine.
 6. The method of claim 1 wherein step(b) further comprises processing the plurality of characteristicparameters using arithmetic capabilities and domain-specific intrinsicsbased on configurable calculation descriptions to express arbitrarilycomplex relationships between the characteristic parameters and tocalculate derived characteristic parameters to be used in determiningthe condition of the machine.
 7. The method of claim 1 wherein step (b)further comprises maintaining cascaded hierarchical statisticalhistories of the characteristic parameters.
 8. The method of claim 7further comprising querying the cascaded hierarchical statisticalhistories of the characteristic parameters to ascertain historicalsimilarity based on minimum, maximum, mean, median, moments, and Z-scorerelative to specified temporal groupings.
 9. The method of claim 7further comprising querying the cascaded hierarchical statisticalhistories of the characteristic parameters to characterize parameterpopulations according to correlation, regression, trend fitting andprojection, and statistical means analysis.
 10. The method of claim 1wherein step (b) further comprises processing the data using analysistechniques selected from the group consisting of windowing, averaging,interpolation and decimation, static and dynamic filters, convolution,peak group signatures, energy distributions, extreme low-frequency,digital integration and differentiation, cross-channel wobble andeccentricity, cross-channel transfer functions, joint time-frequency,cepstrum, wavelets, demodulation, and PeakVue® analytical techniques.11. The method of claim 1 wherein step (c) further comprises operatingon the characteristic parameters to derive the single condition value asan analog value between 0.0 and 1.0, where 0.0 indicates a failedcondition and 1.0 indicates a proper operating condition.
 12. A methodfor reporting an operational condition of a machine to a centralmonitoring system using a machine condition monitoring device, themethod comprising: (a) attaching a plurality of sensors at a pluralityof locations on the machine for sensing operational characteristics atthe plurality of locations; (b) producing a plurality of sensor signalsusing the sensors, the sensor signals indicative of the operationalcharacteristics; (c) acquiring data from the plurality of sensor signalsrelated to the operational characteristics; (d) processing the data tocalculate a plurality of characteristic parameters indicative of theoperational condition of the machine; (e) operating on thecharacteristic parameters to derive a single condition value which isindicative of the operational condition of the machine; and (f)communicating the condition value to the central monitoring system. 13.The method of claim 12 wherein step (e) further comprises operating onthe characteristic parameters to derive the single condition value as ananalog value between 0.0 and 1.0, where 0.0 indicates a failed conditionand 1.0 indicates a proper operating condition.
 14. A machine conditionindication device configured for attachment to a machine for reportinginformation regarding the operational condition of the machine to acentral monitoring system, the device comprising: a plurality of sensorsmounted at a plurality of locations on the machine for sensingoperational characteristics at the plurality of locations and forproducing a plurality of sensor signals indicative of the operationalcharacteristics; a main processor coupled to the plurality of sensorsfor receiving the plurality of sensor signals, for acquiring data fromthe plurality of sensor signals related to the operationalcharacteristics, processing the data to calculate a plurality ofcharacteristic parameters indicative of the operational condition of themachine, and operating on the characteristic parameters to derive asingle condition value which is indicative of the operational conditionof the machine.
 15. The machine condition indication device of claim 14further comprising a communication interface for communicating thecondition value via a communication link to the central monitoringsystem.
 16. The machine condition indication device of claim 15 whereinthe communication interface is further for communicating the conditionvalue via a fieldbus network.
 17. The machine condition indicationdevice of claim 14 further comprising the main processor for acquiringtime waveform data from one or more of the sensors and processing thetime waveform data to calculate the plurality of characteristicparameters.
 18. The machine condition indication device of claim 17further comprising the main processor for acquiring the waveform datafrom more than one of the sensors simultaneously.
 19. The machinecondition indication device of claim 14 further comprising: a digitalsignal processor coupled to a memory subsystem and analog-to-digitalconverters for receiving the data from one or more of the plurality ofsensor signals; and an interface for transferring the data to the mainprocessor.
 20. The machine condition indication device of claim 19wherein the interface further comprises a switched bank of dynamicrandom access memory.
 21. The machine condition indication device ofclaim 14 further comprising the main processor for processing the datato calculate a plurality of waveform-based characteristic parametersselected from the group consisting of mean, minimum, maximum, span,absolute peak, variance, skewness, kurtosis, standard deviation, crestfactor, autocorrelation, and time synchronous correction.
 22. Themachine condition indication device of claim 14 further comprising themain processor for processing time waveform data to calculate frequencyspectral data using discrete Fourier transform techniques selected fromthe group consisting of single-frequency DFT and fast Fourier transform.23. The machine condition indication device of claim 22 furthercomprising the main processor for processing the frequency spectral datato calculate a plurality of frequency-based characteristic parametersselected from the group consisting of peak, phase, power bands, energybands, synchronous energy families, non-synchronous energy, and sidebandenergy families.
 24. The machine condition indication device of claim 23further comprising the main processor for processing the frequencyspectral data to calculate the plurality of frequency-basedcharacteristic parameters using order-based techniques dependent on therotational speed of the machine.
 25. The machine condition indicationdevice of claim 14 further comprising the main processor for processingthe plurality of characteristic parameters using arithmetic capabilitiesand domain-specific intrinsics based on configurable calculationdescriptions to express arbitrarily complex relationships between thecharacteristics, where the configurable calculations descriptions aredownloadable to the device over the communications interface.
 26. Themachine condition indication device of claim 14 further comprising: themain processor for taking N number of data acquisitions from theplurality of sensor signals, for processing the data from the N numberof data acquisitions to calculate N baseline values for each of thecharacteristic parameters, for calculating a representative baselinepair for each of the characteristic parameters based upon the N numberof values, where each baseline pair <A_(base), σ_(base)> comprises abaseline value, A_(base), and a baseline sigma, σ_(base), the mainprocessor for taking N number of new data acquisitions from theplurality of vibration sensor signals subsequent to taking the initialbaseline data acquisitions, for processing the data from the N number ofnew data acquisitions to calculate N number of new values for each ofthe characteristic parameters, for calculating a new pair for each ofthe characteristic parameters based upon the N number of new values,where each new pair <A_(new), σ_(new)> comprises a new value, A_(new),and a new sigma, σ_(new), and for operating on the baseline and newvalues and sigmas according to:if (A_(new)>Min_(diag)) and (A_(new)<A_(base)) then A_(base)=A_(new)andif (σ_(new)>Min_(diag)) and (σ_(new)<σ_(base)) then σ_(base)=σ_(new)where Min_(diag) is a minimum amplitude value of the characteristicparameter which must be exceeded for machine condition analysis to beperformed and which varies according to the operating environment of themachine.
 27. The machine condition indication device of claim 14 furthercomprising the main processor for taking data acquisitions from theplurality of sensor signals, for processing the data from the dataacquisitions to calculate instantaneous values, x_(i), for each of thecharacteristic parameters, and for determining whether eachinstantaneous value, x_(i), of the characteristic parameter for the dataacquisition satisfies the following: $\begin{matrix}{{x_{i}} \notin \left\lbrack {\frac{A_{base}}{N_{\lbrack E\rbrack}},{A_{base} \cdot N_{\lbrack E\rbrack}}} \right\rbrack} & (1) \\{x_{i} \notin \left\lfloor {{A_{base} - {M_{\lbrack E\rbrack}\sigma_{base}}},{A_{base} + {M_{\lbrack E\rbrack}\sigma_{base}}}} \right\rfloor} & (2)\end{matrix}$ where N_([E]) is a parametric amplitude scaling factor andM_([E]) is a parametric sigma scaling factor which define a width of astable region around the baseline value according to the operatingenvironment of the machine.
 28. The machine condition indication deviceof claim 14 further comprising a data storage device for storingconfiguration values, characteristic parameter calculation descriptions,fault similarity inference tables, current baseline data, and historiesof the characteristic parameters.